In Casino Royale, James Bond orders a vodka martini, and is asked, “shaken or stirred?” “Do I look like I give a damn?” he spits back tersely—a clever, if facile, way of signaling that the character had moved on since his early days of fussy tux-wearing and silly gadgetry. Daniel Craig’s 007, we gathered, was to be more of a bruised everyman than the perma-coiffed spy played by his predecessor, Pierce Brosnan. This delighted fans of the franchise, but raised questions about how far from their roots a character could stray.

This past winter, Greta Gerwig tested the limits of this idea with a free-flowing adaptation of Little Women, which essentially rewrote the relationship between Jo and Laurie, and which gave us a wholly new Amy, as played by Florence Pugh. Amy had always b...